This invention relates to a thermal recording medium, particularly to a thermal recording medium which is capable of obtaining a homogeneous and smooth coated surface of a coloring agent layer and obtaining a dye transferred image without irregularity and with high resolving power on a recording sheet such as plain paper.
A thermal recording medium has been used as the recording medium for forming an image by transfer on a recording sheet such as plain paper by means of a thermal printer or thermal facscimile. Such a thermal recording medium has at least one heat-transferable coloring agent layer on a support. A layer containing a coloring agent comprising a dye such as pigment and a heat fusible substance has been known, for example, as the coloring agent layer. As the heat fusible substance, a low melting substance such as wax is used. As the support, in order to obtain good reproducibility of the dye transferred image obtained from the coloring agent layer coated thereon, a film excellent in surface smoothness and dimensional stability has been employed.
The thermal recording medium is produced by providing by coating a coloring agent layer by the hot melt method or the solvent method on such a support which is excellent in surface smoothness and dimensional stability. However, in the case of the coloring agent layer containing a heat fusible substance of the prior art, there is the problem that a coloring agent layer with a constant film thickness and smoothness can be obtained with difficulty. Thus, when the coated surface of the coloring agent layer is non uniform, during letter printing, particular in recording of solid images, irregularity will appear to disadvantageously deteriorate image quality, while the coloring agent layer containing the heat fusible substance of the prior art is poor in transfer efficiency.